Ooooh. The most talked about bad guys or goons in chemistry. Very evil, but not with our teaching. Well let’s start:
Now what exactly is an acid or base? There are many variations but here is the most common.
An acid is a material that can release a proton or hydrogen ion (H+). A base, or alkali, is a material that can donate a hydroxide ion (OH-). That’s what they are.
Now let’s go to the pH scale. What is pH anyway. Many of you may have a pool or a spa and you may have done tests on the water, and most likely pH came up. pH is just a handy way to express how acidic or basic a water solution is. The p means –log, which is a logarithmic function that you should have learned in algebra or calculus. If not, don’t worry, you do not need to know how to calculate pH, but just note that it IS a fundamental part of chemistry. Basically the pH scale ranges from 1 to 14. 1 means most acidic while 14 means most basic. A pH of 7 means neutral, it is neither acidic or basic. Here is the scale:
Now you need to know what are conjugate acids and bases. Let us consider the following reaction:
Now first of all you can tell what is an acid by the H in front of it. If any compound has an H in front of it, it is an acid. Similarly a base will most likely have OH- in it. So above we know that HNO3 is an acid. Now water can act either as an acid or a base. And since HNO3 is an acid water must act as a base here, since acids can’t combine with acids. What happens in this reaction? The H from HNO3 is donated to water, and so it becomes H30 and NO3. Neat huh? Now the product that was an acid but lost its proton (hydrogen ion) is the conjugate base and the one that receives the proton is the conjugate acid. It is kinda screwy wording because it confuses people but that is why the word conjugate is there.
Now there are a list of STRONG acids and bases. Usually strong acids and bases are ones that dissociate in water fully. Here they are:
Strong Acids:
HNO3 - nitric acid
HCl - hydrochloric acid
H2SO4 - sulfuric acid
HClO4 - perchloric acid
HBr - hydrobromic acid
HI - hydroiodic acid
Strong Bases:
LiOH - lithium hydroxide
NaOH - sodium hydroxide
KOH - potassium hydroxide
RbOH - rubidium hydroxide
CsOH - cesium hydroxide
Mg(OH)2 - magnesium hydroxide
Ca(OH)2 - calcium hydroxide
Sr(OH)2 - strontium hydroxide
Ba(OH)2 - barium hydroxide
Note that all alkali metals are fully soluble.